1. Field of the Invention
The present invention relates to an air conditioner operated through the years. In particular, it relates to an improvement of air conditioning ability on an air conditioner capable of conducting a natural circulation operation without using the power of a compressor. Further, the present invention relates to a method for controlling refrigerant for an air conditioner capable of conducting such natural circulation operation as well as a forced circulation operation with the power of a compressor.
2. Discussion of Background
In recent years, a technical field of removing heat from electric machines in a location represented by a computer center or a base station (hereinbelow, referred to as a shelter) accommodating relay electric devices has rapidly spread with spreading of mobile communication such as a portable telephone. Such location is required to conduct an air cooling operation throughout years. In the field of removing from the electric devices requiring an air cooling operation throughout the years, when an outdoor air temperature is low as in a winter season or a night time, it is possible to cool electronic devices by air ventilation. However, a special device for preventing fog, rain, snow, dust and so on from entering therein is necessary. Further, stable air cooling can not be performed because there is variations in an indoor air temperature depending on variations in the outdoor air temperature. Under such conditions, it is possible to use an air conditioner in which natural circulation for carrying heat by refrigerant from an indoor to an outdoor, by utilizing a temperature difference between an indoor air temperature and an outdoor air temperature and a difference of position in height between an indoor unit and an outdoor unit. In the air conditioner utilizing such natural circulation, the power of a compressor is unnecessary when operations utilizing natural circulation (hereinbelow, referred to as natural circulation operation) is to be conducted. Accordingly, it can substantially reduce an annual power consumption in comparison with an air cooling operation by using an air conditioner which conducts operations by using the compressor (hereinbelow, referred to as forced circulation operation).
Now, the operational principle of air cooling operation by the natural circulation will be described with reference to FIG. 17. FIG. 17 is a diagram showing the basic circuit for an air cooling apparatus as an air conditioner utilizing the natural circulation wherein reference numeral 2 designates a condenser, numeral 3 an outdoor fan, numeral 5 an outdoor unit, numeral 6 a liquid pipe, numeral 7 an evaporator, numeral 8 an indoor fan, numeral 9 an indoor unit located in a space to be air-conditioned and numeral 10 a gas pipe. In this case, for conducting air cooling, the evaporator 7 is provided at an indoor side and the condenser 2 is provided at an outdoor side.
The operation will be explained. When the condenser 2 is arranged at a higher position than the evaporator 7, a liquid refrigerant condensed in the condenser 2 descends by the gravity in the liquid pipe 6 to be introduced into the evaporator 7. The liquid refrigerant introduced into the evaporator 7 is vaporized by receiving a thermal load in a space to be air-conditioned, e.g., a room, and then, the vaporized refrigerant ascends in the gas pipe 10 to be returned to the condenser 2; thus, a cycle is formed.
Thus, the air cooling operation by the natural circulation utilizes a density difference between a liquid refrigerant and a gas refrigerant due to a relative position in height between the evaporator 7 and the condenser 2, as a driving force for circulating the refrigerant. The natural circulation can be realized in a case that sum of pressure losses in a refrigerant circuit comprising the condenser 2, the evaporator 7, the liquid pipe 6, the gas pipe 10 and on-off valves in the refrigerant circuit is equal to a pressure increase in the liquid pipe 6 caused by a height of liquid column.
In an air conditioner utilizing such natural circulation, an amount of refrigerant (a refrigerant quantity) to be charged has been determined from experience. Further, a state of the refrigerant has not been properly controlled in consideration of the air conditioning ability during the natural circulation operation.
Further, in an air conditioner utilizing the natural circulation, the existence of a temperature difference between an indoor air temperature and an outdoor air temperature is required. Accordingly, there is a possibility that the natural circulation operation does not function depending on environmental conditions. In this case, an air conditioner capable of effecting the forced circulation operation with use of the compressor in response to the case that the natural circulation operation does not function, is provided. In the air conditioner in combination of the natural circulation operation and the forced circulation operation, it is necessary to provide a refrigerant flow controlling means in the refrigerant circuit from the reasons that there are a variation in a refrigerant flow rate between the natural circulation operation and the forced circulation operation as well as a variation of the refrigerant flow rate due to a variation in the length of a liquid portion, a variation of the refrigerant flow rate derived from a variation of a load, and a difference of a refrigerant quantity derived from the length of the pipes extended in the circuit. In the conventional air conditioners, a reservoir provided at an outlet of the condenser or an accumulator provided at a sucking side of the compressor bore such refrigerant flow controlling function. However, the method for properly controlling a refrigerant quantity has not substantially been conducted.
Conventional Example 1
FIG. 18 is a diagrammatical view of a conventional air cooling apparatus utilizing natural circuit disclosed in JP-A-9-68355. The operation will be described.
In FIG. 18, reference numeral 1 designates a compressor, numeral 2 a condenser, numeral 3 an outdoor fan, numeral 4 an electronic expansion valve, numeral 5 an outdoor unit, numeral 6 a liquid pipe, numeral 7 an evaporator, numeral 9 an indoor unit, numeral 10 a gas pipe, numeral 11 a check valve, numeral 12 a bypass pipe including the check valve 11 and numeral 14 an accumulator. These structural elements are connected with the liquid pipe 6, the gas pipe 10, the bypass pipe 12 and so on to form a refrigerant circuit.
The outdoor unit comprises the compressor 1 to compress a refrigerant gas, the condenser 2 to liquefy the refrigerant gas, the accumulator 14 for preventing the liquid from returning to the compressor 1 in case such as a transient phenomenon, supercharging of refrigerant and so on, and the bypass pipe 12 including the check valve 11 which bypasses the accumulator. The indoor unit 9 comprises the evaporator 7 and the electronic expansion valve 4 which is provided at a position closest to an inlet of the evaporator.
Conventional Example 2
FIG. 19 is a diagrammatical view showing the circuit of an air conditioner for controlling a refrigerant quantity in a cooling/warming apparatus capable of conducting the forced circulation operation and the natural circulation operation, disclosed in JP-A-57-92666. In FIG. 19, reference numeral 1 designates a compressor, numeral 2 a condenser, numeral 5 an outdoor unit, numerals 6, 10 designate refrigerant pipes, i.e. a liquid pipe 6 and a gas pipe 10 used for the natural circulation operation, numeral 7 designates an indoor heat exchanger, numeral 9 an indoor unit, numeral 14 an accumulator, numeral 20 a reservoir, numeral 23 a refrigerant flow controlling device, numeral 24 a dryer filter, numeral 25 a heating device, numeral 26 a refrigerant heating coil, numeral 27 an electromagnetic valve, numeral 28 a check valve, numeral 29 a reverse-flow preventing on-off valve for conducting the starting of warming operation smoothly, numeral 30 a high pressure controlling valve for preventing an abnormal increase of pressure or temperature of the refrigerant at an outlet 26b of the refrigerant heating coil, numeral 31 a capillary pipe, numeral 32 a partition, numeral 33 a refrigerant pipe, numeral 34 a branch, numeral 35 a pipe, numeral 36 an electric heater, and numerals 37, 38 designate on-off valves.
In the air conditioner, when the forced circulation operation is conducted by using the compressor 1, the electromagnetic valve 27 is closed to form a closed circuit comprising the compressor 1, the condenser 2, the dryer filter 24, the check valve 28, the capillary pipe 31, the refrigerant pipe 6, the indoor heat exchanger 7, the refrigerant pipe 10 and the accumulator 14 of the refrigerant flow controlling device 23 wherein the indoor heat exchanger 7 is operated as an evaporator whereby cooling is effected by utilizing the evaporation of the refrigerant.
On the other hand, in a case of warming by the natural circulation operation, the electromagnetic valve is opened and the heating device 25 is operated to thereby form a closed circuit comprising the refrigerant heating coil 26, and end portion 26a at a higher position side of the coil, the electromagnetic valve 27, the accumulator 14, the refrigerant pipe 10, an end portion 7a at a higher positional side of the indoor heat exchanger, the indoor heat exchanger 7, an end portion 7b at a lower position side of the indoor heat exchanger, the refrigerant pipe 6 and an end portion 26b at a low position side of the refrigerant heating coil 6. Then, the indoor heat exchanger 7 is operated as a condenser whereby warming is conducted by utilizing the condensation of the refrigerant.
The inside of the refrigerant flow controlling device 23 is divided to an outside room 20 and an inside room 14 with the partition 32. The outside room 20 influenced by an outdoor air temperature is used as a reservoir and the inside room 14 is as an accumulator. The branch pipe 34 communicates a bottom portion of the reservoir 20 with the refrigerant pipe 33.
The refrigerant pipe 33 connected to the reservoir 20 by means of the branch pipe 34 is a pipe in which a liquid refrigerant of low pressure is passed to the indoor heat exchanger 7 in the forced circulation operation, and it is also a pipe in which the liquid refrigerant after having subjected to heat exchanging in the indoor heat exchanger 7 in the natural circulation operation is passed therethrough.
The accumulator 14 constitutes a refrigerant pipe through which a gas refrigerant after having subjected to heat exchanging in the indoor heat exchanger 7 in the forced circulation operation is passed and a refrigerant pipe through which the gas refrigerant to be supplied to the indoor heat exchanger 7 in the natural circulation operation is passed. A difference in refrigerant quantity between the forced circulation operation and the natural circulation operation is adjusted by the refrigerant flow controlling device 23.
In the above mentioned conventional air conditioners, when an outdoor air temperature is lower than a predetermined value, for example, 5xc2x0 C. in the natural circulation operation, it is necessary to increase a refrigerant flow rate because an air conditioning load is increased. However, the refrigerant tends to accumulate in the refrigerant controlling device 23 because the refrigerant controlling device 23 is cooled by outdoor air. In such case, the electric heater 36 is actuated to generate heat by an instruction from an outdoor air temperature detecting thermostat that the refrigerant flow controlling device 23 so that the accumulated refrigerant is vaporized. Accordingly, a refrigerant quantity in the refrigerant flow controlling device 23 can properly be maintained even though an outdoor air temperature is low, and a sufficient natural circulation ability can be obtained.
As described above, in the conventional air conditioners utilizing the natural circulation, a refrigerant quantity to be charged was roughly determined without considering the air conditioning ability. Further, there was no attempt to improve the air conditioning ability by controlling a state of the refrigerant in the natural circulation operation.
Further, in the conventional air conditioners capable of effecting the forced circulation operation and the natural circulation operation, when an outdoor air temperature became lower than a set value in a case that the refrigerant quantity in the natural circulation operation was controlled in response to a change of an air conditioning load, the electric heater 36 was made to be conductive by an instruction from the outdoor air temperature detecting thermostat to thereby generate heat whereby a predetermined quantity of heat was given to the refrigerant flow controlling device 23. In the conventional air conditioners, since the control of the refrigerant quantity was not conducted in consideration of how an outdoor air temperature or a refrigerant flow rate influences the ability in the natural circulation operation, there was a problem that an effect of reducing consumption power by utilizing the natural circulation operation became small.
Further, since the adjustment of the refrigerant quantity was conducted by the electric heater, there is substantial power consumed by the electric heater. Further, there was a problem that an effect of reducing consumption power by utilizing the natural circulation operation became small.
It is an object of the present invention to provide a method for determining a charging amount of refrigerant for an air conditioner utilizing a natural circulation wherein the optimum amount of refrigerant can be charged in consideration of the air conditioning ability while providing the maximum ability of the air conditioner.
Further, it is an object of the present invention to provide a method for controlling refrigerant for an air conditioner capable of conducting a natural circulation operation wherein the optimum state of refrigerant can be provided in consideration of the air conditioning ability while performing the maximum air conditioning ability.
Further, it is an object of the present invention to provide a method for controlling refrigerant for an air conditioner capable of conducting a forced circulation operation and a natural circulation operation wherein the forced circulation operation can smoothly be switched to the natural circulation operation without requiring an external input such as electric heater, and consumption power can substantially be reduced.
Further, it is an object of the present invention to provide a method for controlling refrigerant for an air conditioner capable of conducting a forced circulation operation and a natural circulation operation wherein the forced circulation operation can smoothly be switched to the natural circulation operation without requiring an external input such as an electric heater, the natural circulation operation can be conducted by utilizing the air conditional ability to the maximum, and consumption power can substantially be reduced.
Further, it is an object of the present invention to provide an air conditioner which provides a high air conditioning ability in a natural circulation operation.
In accordance with a first aspect of the present invention, there is provided a method for determining a charging amount of refrigerant for an air conditioner which conducts a natural circulation operation by circulating refrigerant through an evaporator and a condenser located at a higher position than the evaporator, which are connected with pipes, said method being characterized by comprising means for obtaining an air conditioning load quantity to an outdoor air temperature among outdoor air temperatures, means for obtaining an air conditioning ability quantity to an outdoor air temperature in a temperature range in a case of using a predetermined quantity of refrigerant, means for obtaining the maximum outdoor air temperature capable of conducting air conditioning at the time when an air conditioning load quantity produced from the means for obtaining an air conditioning load quantity substantially coincides with an air conditioning ability quantity from the means for obtaining an air conditioning ability quantity in using a predetermined quantity of refrigerant, and means for obtaining respective maximum outdoor air temperatures capable of conducting air conditioning when said predetermined quantity of refrigerant is changed and for determining a refrigerant quantity, as an amount to be charged, in which a maximum outdoor air temperature capable of conducting air conditioning among the obtained maximum outdoor air temperatures becomes the maximum.
In accordance with a second aspect of the present invention, there is provided a method for controlling refrigerant for an air conditioner capable of switching between a forced circulation operation for circulating refrigerant through a compressor, a condenser, a refrigerant flow controlling means, an evaporator and a refrigerant storing means which are connected successively with pipes and a natural circulation operation for circulating the refrigerant through a bypass pipe for bypassing the compressor and the refrigerant storing means, the condenser, the refrigerant flow controlling means and the evaporator which are connected, said method being characterized by comprising, at the time of switching from the forced circulation operation to the natural circulation operation, means for making the refrigerant in an outlet portion of the evaporator to be a superheat state, and means for introducing a refrigerant gas in a superheat state into the refrigerant storing means to vaporize the refrigerant stored in the refrigerant storing means whereby the refrigerant stored in the refrigerant storing means during the forced circulation operation is recovered into a refrigerant circuit for the natural circulation operation.
Further, there is provided the method for controlling refrigerant for an air conditioner according to the second aspect, wherein the refrigerant flow controlling means is controlled by said means for making the refrigerant in the outlet portion of the evaporator to be a superheat state so that the refrigerant flow rate is smaller than a refrigerant flow rate in the forced circulation operation.
In accordance with a third aspect of the present invention, there is provided a method for controlling refrigerant for an air conditioner capable of switching between a forced circulation operation for circulating refrigerant through a compressor, a condenser, a refrigerant flow controlling means, an evaporator and a refrigerant storing means which are connected successively with pipes and a natural circulation operation for circulating the refrigerant through a bypass pipe for bypassing the compressor and the refrigerant storing means, the condenser, the refrigerant flow controlling means and the evaporator which are connected, said method being characterized by comprising, at the time of switching from the forced circulation operation to the natural circulation operation, a refrigerant vaporizing means for vaporizing the refrigerant stored in the refrigerant storing means, means for detecting a temperature difference between an outdoor temperature and a set temperature set for air conditioning, and means for changing an evaporation quantity on the refrigerant depending on the magnitude of a temperature difference detected by the temperature difference detecting means in the evaporation of the refrigerant by the refrigerant vaporizing means, whereby a quantity of recovery of the refrigerant stored in the refrigerant storing means in the forced circulation operation is increased or decreased as a result that a refrigerant quantity in the refrigerant circuit in the natural circulation operation is increased or decreased.
In accordance with the present invention, there is provided the method for controlling refrigerant for an air conditioner according to the third aspect wherein a part of a superheated gas discharged from the compressor is introduced into the refrigerant storing means along with the superheated gas from the evaporator by means of a refrigerant vaporizing means on the refrigerant stored in the refrigerant storing means whereby the refrigerant stored in the refrigerant storing means is vaporized.
In accordance with the present invention, there is provided the method for controlling refrigerant for an air conditioner according to the third aspect, wherein the refrigerant vaporizing means is operated for a predetermined time to vaporize the refrigerant stored in the refrigerant storing means.
In accordance with the present invention, there is provided the method for controlling refrigerant for an air conditioner according to the third aspect, wherein the refrigerant vaporizing means is operated on the refrigerant stored in the refrigerant storing means so that a degree of superheating in the outlet portion of the evaporator reaches a predetermined degree of superheating.
In accordance with a fourth aspect of the present invention, there is provided a method for controlling refrigerant for an air conditioner which conducts a natural circulation operation by circulating refrigerant through an evaporator and a condenser located at a higher position than the evaporator, which are connected with a pipe, said method being characterizing in that in the natural circulation operation, at least one of a refrigerant flow rate, an air flow rate to the evaporator and a refrigerant quantity in the evaporator is changed so that a degree of superheating or a degree of dryness of the refrigerant in an outlet portion of the evaporator becomes a predetermined value.
In accordance with the present invention, there is provided the method for controlling refrigerant for an air conditioner according to the fourth aspect, wherein values to be set for the refrigerant in the outlet portion of the evaporator in the natural circulation operation are a value of not less than 0.9 in terms of a degree of dryness and a value of not more than 10xc2x0 C. in terms of a degree of superheating.
In accordance with the present invention, there is provided the method for controlling refrigerant for an air conditioner according to the fourth aspect, wherein at least one of the refrigerant flow rate, the air flow rate to the condenser and the refrigerant quantity in the condenser is changed so that a degree of supercooling or a degree of dryness of the refrigerant in the outlet portion of the condenser in the natural circulation operation becomes a predetermined value.
In accordance with the present invention, there is provided the method for controlling refrigerant for an air conditioner according to the fourth aspect, wherein values of the refrigerant in the outlet portion of the condenser in the natural circulation operation are not more than 0.1 in terms of a degree of dryness and not more than 20xc2x0 C. in terms of a degree of supercooling.
In accordance with the present invention, there is provided the method for controlling refrigerant for an air conditioner according to the fourth aspect, wherein at least one of the refrigerant flow rate, the air flow rate and the refrigerant quantity in the natural circulation operation is changed with predetermined time intervals.
In accordance with the present invention, there is provided the method for controlling refrigerant for an air conditioner according to the fourth aspect, wherein at least one of the refrigerant flow rate, the air flow rate and the refrigerant quantity in the natural circulation operation is changed when a temperature difference between an outdoor air temperature and a predetermined set temperature for air conditioning is not more than 25xc2x0 C.
In accordance with a fifth aspect of the present invention, there is provided an air conditioner comprising an evaporator and a condenser located at a higher position than the evaporator, which is connected to the evaporator with a pipe to conduct a natural circulation operation by circulating refrigerant, said air conditioner being characterized by comprising a refrigerant state detecting means for detecting a state of the refrigerant in an outlet portion of the evaporator in the natural circulation operation, a refrigerant flow controlling means for controlling a refrigerant flow rate in circulation and a controlling means for controlling the refrigerant flow controlling means depending on a state of the refrigerant detected by the refrigerant state detecting means to change the refrigerant flow rate.
In accordance with the present invention, there is provided the air conditioner according to the fifth aspect, which further comprises a refrigerant storing means for storing an excessive amount of the refrigerant resulted from the controlling of the refrigerant flow rate.
In accordance with the present invention, there is provided the air conditioner according to the fifth aspect, wherein the refrigerant state detecting means is to detect a degree of superheating or a degree of dryness of the refrigerant in the outlet portion of the evaporator.
In accordance with the present invention, there is provided the air conditioner according to the fifth aspect, wherein the refrigerant state detecting means is to detect a degree of supercooling or a degree of dryness of the refrigerant in the outlet portion of the condenser, and the controlling means is to operate the refrigerant flow controlling means to change the refrigerant flow rate depending on a temperature difference between an outdoor air temperature and the set temperature set for air conditioning and a state of the refrigerant.
In accordance with a sixth aspect of the present invention, there is provided an air conditioner capable of switching between a forced circulation operation for circulating refrigerant through a compressor, a condenser, a refrigerant flow controlling means, an evaporator and a refrigerant storing means which are connected successively with pipes and a natural circulation operation for circulating the refrigerant through a bypass pipe for bypassing the compressor, the condenser located at a higher position than the evaporator, the refrigerant flow controlling means and the evaporator which are connected, said air conditioner being characterized in that the refrigerant flow controlling means is located in a space where the evaporator is located.